1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) and a method of driving the same, and more particularly, relates to driving an LCD using one or more polarity inversion methods.
2. Description of the Related Art
Liquid crystal displays (LCDs) control transmittances in liquid crystal cells in accordance with data signals to display an image. The LCD often includes a liquid crystal panel on which the liquid crystal cells are arranged in a matrix and a driving circuit for driving the liquid crystal panel.
FIG. 1 is a block diagram illustrating a conventional LCD.
Referring to FIG. 1, the conventional LCD includes a liquid crystal panel 2 on which the liquid crystal cells are arranged in a matrix, a gate driver 4 for driving gate lines GL1 to GLn of the liquid crystal panel 2, and a data driver 6 for driving data lines DL1 to DLm of the liquid crystal panel 2.
The liquid crystal panel 2 includes thin film transistors (TFT) formed at the crossing regions of the n gate lines GL1 to GLn and the m data lines DL1 to DLm.
The TFTs are used to control whether data signals from the data lines DL1 to DLm are provided to the liquid crystal cells in response to gate signals from the gate lines GL1 to GLn.
The liquid crystal cells can be equivalently represented by liquid crystal capacitors Clc including common electrodes that face each other with liquid crystal interposed and pixel electrodes coupled with the TFTs. A storage capacitor (not shown) for maintaining the voltage of a data signal stored in the liquid crystal capacitor until a next data signal is supplied, is further formed in each of the liquid crystal cells. The storage capacitor can be formed between the gate electrode and the pixel electrode.
The gate driver 4 sequentially supplies gate signals to the gate lines GL1 to GLn so that the TFTs coupled with the corresponding gate lines are driven.
The data driver 6 converts digital data to analog data signals and supplies video signals for one horizontal line to the data lines DL1 to DLm in one horizontal period where the gate signals are supplied to the gate lines GL. The data driver 6 converts the digital data into data signals using gamma voltages supplied from a gamma voltage generator (not shown) to generate the data signals.
In order to prevent the liquid crystal cells from deteriorating and to improve picture quality, in driving the liquid crystal cells on the liquid crystal panel, an inversion method is often used. The inversion method generally includes a frame inversion method, a line inversion method, a column inversion method, or a dot inversion method.
In the frame inversion method, the polarity of video signals supplied to the liquid crystal cells on the liquid crystal panel is inverted whenever a frame is changed. However, since the data signals of the same polarity are supplied to an entire frame, it is not advantageous in preventing liquid crystal cells from deteriorating.
In addition, in the line inversion method, the polarity of the data signals supplied to the liquid crystal panel is inverted in each of the gate lines on the liquid crystal panel and in each frame as illustrated in FIGS. 2A and 2B. In such case, crosstalk often exists between horizontal pixels. Consequently, flicker in the form of stripes is generated between horizontal lines. In addition, an alternating current (AC) voltage source having a predetermined driving frequency is often used. As a result, the LCD display using the line inversion method produces vibration causing audible noise.
In the column inversion method, the polarity of the video signals supplied to the liquid crystal panel is inverted in the data lines on the liquid crystal panel and in each frame as illustrated in FIGS. 3A and 3B. Crosstalk is often generated between vertical pixels. The crosstalk causes flicker in the form of stripes between vertical lines.
In the dot inversion method, as illustrated in FIGS. 4A and 4B, video signals of opposite polarities are supplied to all of the horizontally and vertically adjacent liquid crystal cells such that the polarity of the video signals is inverted in each adjacent frame. Since flicker generated between the vertically and horizontally adjacent pixels is offset, higher quality image is produced using the dot inversion method in comparison with the other inversion methods.
However, in the dot inversion method, the polarity of the data signals supplied from the data driver to the data lines is horizontally and vertically inverted. Therefore, since the change in pixel voltage and frequency from one pixel to another is larger than the change in the other inversion methods, power consumption increases.